MR2 fixed issues
"In BlackBerry Enterprise Server version 5.0, in certain circumstances, a search for all user accounts might have returned the error message “The request could not be completed.”
In BlackBerry Enterprise Server version 5.0 MR1, this issue is resolved."

i guess oh no it isnt

This isn't the same problem you have. That issue was most certainly fixed with MR1.
Yours is different.